Let us consider a mobile unit that moves along a track with a variable tilt. As an example, one can envision a farm tractor towing an implement, like a spray unit, in a field.
If the mobile unit equipped with a satellite navigational system (for example, GPS) moves along a track with variable tilt, the GPS feeds positions into the guidance system. As the mobile unit travels the rough terrain, crosstrack error is introduced into the guidance system, because when the GPS is out of track, the mobile unit itself is on the track with variable tilt.
Thus, the actual coordinates of the mobile unit is difficult to determine using only the satellite navigational system without knowledge of the crosstrack error.
What is needed is a satellite navigational system integrated with a tilt measurement system that is capable of precise measurement of the coordinates of the mobile unit that moves along a variable tilt track.